This invention resides broadly in the field of electronic musical instruments, and is particularly adaptable for use in instruments employing a demultiplexing audio waveshape generator.
The principles of the present invention are applicable to various electronic musical instruments in which musical sounds are generated in response to actuation of key switches regardless of whether those switches are actuated directly, e.g., by the musician's fingers, or indirectly, e.g., by the plucking of strings. The term key is used in a generic sense, to include depressible levers, actuable on-off switches, touch or proximity responsive devices, closable apertures and so forth. The present invention relates to the attack and decay characteristics of a musical note placed on an electronic musical instrument. More particularly, the present invention relates to a two-part attack and decay system, either part of which may also be used independently of the other for an electronic musical instrument.
The function of an electronic musical instrument is to reproduce or simulate the notes of a musical scale by electronic means. In order to provide other than an abrupt start with an abrupt end of the tone envelope generated when a particular key is depressed and released, respectively, it is desirable to simulate tone attack and decay by gradually increasing the tone amplitude at the leading edge and gradually decreasing the amplitude at the trailing edge.
Heretofore, the systems used either analog or digital envelope signals which were applied to a scaler for controlling the relative note amplitudes from zero to maximum value. Typically in an analog instrument, this scaling was accomplished through an amplitude control such as keyers or a voltage controlled amplifier and in a digital instrument the scaling was typically accomplished using a digital multiplier. Such prior art attack and decay systems were complicated and required extensive hardware. The present invention provides the advantages of being simple and cost effective.